1. Technical Field of the Invention
The present invention is directed to methods and systems in wireless user terminals, such as mobile smart phones, for detecting wireless networks and determining when to use the current network or select other wireless networks for communication. Using real-time information about wireless network performance conditions and historical wireless network performance information along with network operator policies, the decision to use one wireless network service over another can be optimized to provide an improved end user experience.
2. Description of the Prior Art
Cellular networks generally consist of two main parts: the radio access subsystem and the core network. The rapid increase of data usage and resulting network congestion give rise to the need for integration of multiple radio access (wireless) technologies other than the traditional cellular radios (most notably—WLAN or WiFi). The industry is taking various steps to facilitate this by incorporating WLAN and other access techniques in mobile terminals and building internetworking solutions to allow session persistence while connecting an ongoing “call” between various access technologies etc.
WLAN (e.g., WiFi) has recently become the alternate network of choice for data offloading. However, due to some fundamental differences between traditional cellular technology and WLAN, incorporating WLAN into the mix of “legitimate” access technologies serving the mobile networks has few unique challenges. WLAN transmission power is severely limited in comparison to its cellular counterpart; consequently WLAN radio coverage is rather limited and normally would not go beyond few tens of meters. To provide acceptable WLAN coverage one must deploy much larger amount of WLAN access points then done in cellular deployment. Higher deployment density (larger number of deployment sites) results with higher maintenance cost thereby defeating the purpose of lowering service cost. Unlike cellular technology that operates in a “private” (licensed) spectrum, WLAN needs to function within hostile conditions of unlicensed spectrum; radio interference is uncontrolled in these spectrum bands. Consequently operators find it very difficult to assure an acceptable quality of service (QoS) putting in question the use of WLAN altogether.
The common WLAN solution offered to operators is basically replicating cellular operator's deployment. Companies are deploying WLAN access points at specific locations where they expected increase data traffic (hotels, airports, large stores etc.). This solution could be adequate when user terminals were mostly laptops that are not very mobile. The deployed networks are managed using traditional network/cellular management techniques. As mentioned above, providing highly ubiquitous WLAN coverage using this approach is not practical due to maintenance cost considerations.
As time progresses, much higher mobility devices are becoming common; smart-phones such as iPhone and Android devices are rapidly becoming main data traffic contributors hence the selected locations model is quickly becoming obsolete. The need for ubiquitous WLAN coverage is growing further challenging the operator's style deployment.
The industry, through its standardization process, has been defining a new core network function to support heterogeneous radio access environment: the Access Network Discovery and Selection Function (ANDSF). The ANDSF is aimed to guide mobile terminals in finding alternate access networks and select the most suitable network for best service. Currently, the ANDSF is designed to support locating “carrier WLAN” and selecting the access network based on administrative policies. For example—connect to WLAN if there is a roaming agreement with the WLAN owner. No mechanism has been defined to dynamically improve the effectiveness of these policies by testing their impact on service quality or performance. This shortcoming is especially critical when dealing with WLAN where operation environment is less predictable due to the issues mentioned above.
Currently there is no way to enable a device to execute a policy based on anticipated QoS needs, for example: Connect to WLAN only if the WLAN is currently likely to provide a good service, and the cellular network is likely to be congested now. Furthermore, the likelihood of having the WLAN access option at any time is rather small due to the limited coverage provided by the “carrier WLAN” due to economical constrains as explained above. Therefore data offloading using carrier WLAN may not be very effective.
To avoid QoS problems, it has been suggested to let the mobile terminal decide which network to prefer based on “local snooping”. For example, a mobile terminal can sequentially connect to each of the access networks in reach and evaluate their data speed capability. This method will consume a substantial amount of time and will be highly inaccurate as the short term signal and load fluctuations may cause erroneous decision. These operations may require substantial amount of connections (switching connections) and even then, the decision will be sub-optimal. Frequent connection alterations can easily overload the network's control plan (“ping-pong”) resulting with horrible user experience. This application proposes an enhancement to ANDSF to improve network selection and specifically increase WLAN availability and connection quality.
Excerpts from 3GPP Standards Regarding ANDSF
This section provides for an overview of 3GPP requirement for ANDSF. The following is an extract from TS23.402.
The ANDSF contains data management and control functionality necessary to provide network discovery and selection assistance data as per operators' policy. The ANDSF shall respond to UE requests for access network discovery information (pull mode operation) and may be able to initiate data transfer to the UE (push mode operation), based on network triggers or as a result of previous communication with the UE.
The ANDSF shall be able to provide the following information:                1) Inter-system mobility policy:                    The inter-system mobility policy is a set of operator-defined rules and preferences that affect the inter-system mobility decisions taken by the UE. The UE uses the inter-system mobility policy when it can route IP traffic only over a single radio access interface at a given time (e.g. is not IFOM capable or its IFOM capability is disabled) in order to:                        (i) decide when inter-system mobility is allowed or restricted; and        (ii) to select the most preferable access technology type or access network that should be used to access EPC.                    For example, an inter-system mobility policy may indicate that inter-system handover from E-UTRAN access to WLAN access is not allowed. It may also indicate e.g. that WiMAX access is more preferable to WLAN access.            The inter-system mobility policy may be provisioned in the UE and may be updated by the ANDSF based on network triggers or after receiving a UE request for network discovery and selection information.            The inter-system mobility policy identifies which access technology type or which specific access network is mostly preferable for EPC access. It shall be able to indicate:            If a specific access technology type is preferable to another (e.g. WiMAX is preferable to WLAN).            If a specific access network identifier is preferable to another (e.g. WLAN SSID-1 is preferable to WLAN SSID-2).            The inter-system mobility policy identifies also when inter-system mobility is allowed or restricted. It shall be able to indicate:            If inter-system mobility is restricted from one access technology type to another (e.g. handover from WiMAX to WLAN is restricted).            If inter-system mobility is restricted when certain conditions are met.            Validity conditions, i.e. conditions indicating when a policy is valid (such conditions may include e.g. a time duration, a location area, etc.). The validity conditions may also indicate when the UE shall request for new policies.            The inter-system mobility policy indicates whether the operator-preferred list of access networks or access technology types for EPC access, shall take precedence over corresponding user-preferred list, when automatic access network selection is used.                        2) Access network discovery information:                    Upon UE request, the ANDSF may provide a list of access networks available in the vicinity of the UE for all the access technology types requested by the UE (if any requested).            The ANDSF provides information for access networks that are available to the UE including:            the access technology type (e.g. WLAN, WiMAX).            the radio access network identifier (e.g. the SSID of a WLAN).            other technology specific information, e.g. one or more carrier frequencies.            validity conditions, i.e. conditions indicating when the provided access network discovery information is valid (such conditions may include e.g. a location).            The UE may retain and use the access network discovery information provided by the ANDSF until new/updated information is retrieved.                        3) Inter-System Routing Policy:                    The ANDSF may provide a list of Inter-System Routing Policies to UEs that are capable of routing IP traffic simultaneously over multiple radio access interfaces. The UE uses the inter-system routing policies when it can route IP traffic simultaneously over multiple radio access interfaces (e.g. it is an IFOM capable UE with the IFOM capability enabled) in order to meet the operator routing/offload preferences by:                        (i) deciding when an access technology type/access network is restricted for a specific IP traffic flow and/or a specific APN; and        (ii) selecting the most preferable access technologies/access networks and/or APNs which shall be used by the UE when available to route IP traffic that matches specific criteria (e.g. all traffic to a specific APN, or all traffic belonging to a specific IP flow, or all traffic of a specific application, etc).                    The inter-system routing policy may be provisioned in the UE and may be updated by the ANDSF based on network triggers or after receiving a UE request for network discovery and selection information.            Each inter-system routing policy includes the following information:            Validity conditions, i.e. conditions indicating when the provided policy is valid.            One or more Filter Rules, each one identifying a prioritized list of access technologies/access networks which shall be used by the UE when available to route traffic that matches specific IP filters and/or specific APNs. A filter rule also identifies which radio accesses are restricted for traffic that matches specific IP filters and/or specific APNs (e.g. WLAN is not allowed for traffic to APN-x).            A Filter Rule may also identify which traffic shall or shall not be non-seamlessly offloaded to a WLAN when available, if the UE supports the non-seamless WLAN offload capability specified in clause 4.1.5.                        
There are three types of information provided by the ANDSF, i.e. the inter-system mobility policy, the access network discovery information and the inter-system routing policy. The ANDSF may provide all types of information or only one of them. The user may manually select the access technology type or access network that should be used by the UE; in such a case the inter-system mobility policies are not taken into account.
UE with ANDSF Requirements
If the UE has access to network discovery information, inter-system mobility policies or inter-system routing policies are valid for its present location, which indicate that there is an access network in its vicinity with higher priority than the currently selected access network(s), the UE should perform procedures for discovering and reselecting the higher priority access network, if this is allowed by user preferences.
A UE that is not capable of routing IP traffic simultaneously over multiple radio access interfaces (e.g. a non-IFOM or non-MAPCON capable UE, or a UE not capable of non-seamless WLAN offload) shall select the most preferable available access network for inter-system mobility based on the received/provisioned inter-system mobility policies and user preferences. When automatic access network selection is used, the UE shall not initiate a connection to the EPC using an access network indicated as restricted by inter-system mobility policies. When the UE selects a non-3GPP radio access as indicated by the preferences in the inter-system mobility policies, the UE may still use 3GPP access for CS services.
A UE that is capable of routing IP traffic simultaneously over multiple radio access interfaces (i.e. an IFOM or MAPCON capable UE, or a UE capable of non-seamless WLAN offload) may be pre-provisioned with or shall be able to receive from the ANDSF (if the UE supports communication with ANDSF) both inter-system mobility policies and inter-system routing policies. When the UE has the IFOM, the MAPCON and the non-seamless WLAN offload capabilities disabled, the UE shall select the most preferable available access network based on the received/provisioned inter-system mobility policies and user preferences. When the UE has the IFOM or MAPCON or non-seamless WLAN offload capability enabled, the UE shall select the most preferable available access networks based on the received/provisioned inter-system routing policies and user preferences. In addition, the UE shall route traffic that matches specific criteria according to the filter rules in the received/provisioned inter-system routing policies and according to the user preferences.
When roaming, it shall be possible for the UE to resolve potential conflicts between the policies provided by the Home ANDSF (H-ANDSF) and the policies provided by the Visitor ANDSF (V-ANDSF). This applies to both the inter-system mobility policies and to the inter-system routing policies.
The ANDSF shall be able to limit the amount of information provided to the UE based e.g. on the UE's current location, UE capabilities, etc. The ANDSF shall be able to limit the load caused by the UE initiated requests towards the ANDSF.
The H-ANDSF in the subscriber's home operator network may interact with other databases such as the HSS user profile information residing in subscriber's home operator network. Details of such interaction with these databases are not described in this Release of the specifications.
Inter-system mobility policies, access network discovery information and inter-system routing policies may also be statically pre-configured by the operator on the UE. The inter-system mobility policies, access network discovery information and inter-system routing policies provided to the UE by the ANDSF take precedence on the inter-system mobility policies, access network discovery information and inter-system routing policies pre-configured on the UE.
ANDSF/UE Communication Protocol
The protocol between ANDSF server to Client is based on OMA Device Management Protocol—“OMA-TS-DM_Protocol-V1—2-20060602-C”
The OMA Device Management Protocol allows management commands to be executed on nodes. It uses a package format similar to SyncML Synchronization Protocol [SYNCPRO] and SyncML Representation Protocol [REPPRO]. A node might reflect a set of configuration parameters for a device. Actions that can be taken against this node might include reading and setting parameter keys and values. Another node might be the run-time environment for software applications on a device. Actions that can be taken against this type of node might include installing, upgrading, or uninstalling software elements.
Actions are represented by OMA Device Management Protocol Commands, which are described in [REPPRO] and Device Management Usage [DMREPU]. The commands and message structure used correspond identically to that of the [SYNCPRO]. Thus, the DTD for the Management Protocol is the DTD from [SYNCPRO].